AccumulatorState cannot have other methods

[kaikalur]

Currently, AccumulatorState has exactly one method getEstimatedSize. And this is codegen'd in the accumulator compiler which just hard codes that one method and tries to produce class with state for other get/is/set functions like Java beans. This is too subtle and brittle. We should have add an annotation or something in case there is a need for non-serializable parts in the AccumulatorState